Inhibitors of oxidation of phenols



INHIBITORS OF OXIDATION OF PHENOLS Harry Clough, Norton-on -Tees, England, assignor, to

Imperial Chemical Industries Limited, London, England, a corporation of Great Britain Application May 7, 1956 Serial No. 582,938

Claims priority, application Great Britain May 16, 1955 6 Claims. (Cl. 260-620) No Drawing.

lieved to be accelerated by the presence of metal impurities. Since the commercial value of phenols and alkylated phenols is often greatly dependent upon freedom from colour and the absence of unpleasant odour, it

is important to provide means to prevent or greatly minimise the development of these deleterious features.

We have found that the oxidation of phenols and their alkylated derivatives leading to the formation of coloured compounds and/or compounds having an unpleasant odour can be inhibited by the presence of a small amount of one or more Schitfs Bases as hereinafter de- I According to the present invention, therefore, we provide a process of inhibiting the formation by oxidation of coloured compounds and/ or compounds having an unpleasant odour in phenols and their alkylated derivatives which comprises the step of adding a small amount of at least one Schiffs Base of the type hereinafter defined.

Also according to the present invention there is provided a new composition of matter which comprises at least one phenol or alkylated derivative thereof which is liable to oxidation leading to the formation of highlycoloured and/or unpleasantly odoriferous compounds, and a small amount of at least one Schiifs Base of the type hereinafter defined.

By a Schifis Base, we mean, in this specification, a compound having the formula:

in which R comprises an aliphatic chain having the nitrogen atoms shown attached to two different carbon atoms of the aliphatic chain, and A and A are aromatic nuclei, or 5- or 6-membered heterocyclic nuclei having nitrogen as the heterocyclic atom or atoms, and having each OH group shown attached to a position on the nucleus A or A, which is adjacent to the corresponding --CH=N- group. A and A; can be identical, or different groups, and may for example be phenylene nuclei.

By a small amoun we means, in this specification, an amount which is at most approximately 1% by weight of the phenols or alkylated phenols with which the Schitfs Base compounds are admixed, and preferably 0.1% to 1% by weight.

It is preferred that the aliphatic chain R is a saturated aliphatic chain. A suitable saturated aliphatic chain is, for example, the ethylene radical CH CH Suitable phenols which may be stabilised by the process of the present invention include for example monohydroxy phenols such as phenyl phenols and alkyl phenols,

, 2,872,490 Patented Feb. 3, 1959 2 in particular, or'tho phenylphenol, para phenylphenol, and 4-methyl-2,6-di-tert. butyl phenol.

The components of the compositions of matter of the present invention may be admixed in any convenient way. For example, they may be mixed, as in the following example, by precipitation of the phenol compounds in the presence of the Schifis Base compounds.

It is a feature of the present invention that the inhibiting effect of the added Schiifs Base compounds persists even though the alkyl phenols to which they are added then undergo for example washing or recrystallisation treatments which might be expected to removeany of the added Schilfs Bases. These inhibitors can therefore be added to the alkyl phenols at any convenient stage, and not necessarily during the final treating steps. This is an advantage, since it may be preferable to carry out the final treating steps some considerable time after the initial production of the alkyl phenols, during which time coloured and/or unpleasantly odoriferous compounds might be formed if the Schifls Bases of the invention were not present during some part of the early stages for two samples of 4-methyl-2,6-di-tertiary butylphenol, one sample of which was treated with disalicylidene-- ethylenediamine. The colour development was measured in Lovibond units according to the standard S. T. P. T. C.

test No. C. C. 1350 using 1" cells, and recorded accord- I ing to the formula:

where C=colour, Y=number of yellow units used and R=number of red units used. The samples for the present example were obtained as follows. I

300 mls. of a mixture of alkylated phenols containing 70 to 4-methyl-2,6-di-tertiary butylphenol was added at 70 C. to a mixture of 510 mls. of methanol and mls. of water and cooled for approximately one hour at 10-15 C. The precipitate which formed was substantially 4-methyl-2,6-di-tertiary butylphenol and was removed by centrifuge, dried under reduced pressure at 35 to 40 C., and stored in the dark at room temperature.

A second batch of 300 mls. of the alkylated phenols was treated in exactly the same way except that the methanol-water mixture also contained a quantity of disalicylidene ethylene diamine corresponding to 0.1% by weight of the alkylated phenols to be added to the methanol-water mixture.

The following table gives the colour changes observed in the two samples, stored under identical conditions and tested according to the above method.

Table 1 Colour of Sample Additive Weeks storage Nll l. l 3. l 1. 5

5. 0 Disallcylidene ethylenediamine 1.1 1. 7

EXAMPLE 2 3 Table 2 Colour of Sample Additive Days Storage N11; 2.4 17.4, 18.6 23.4 30.3 Disalleylldene' ethyle'nedlainlrie- 1.5 1.2 1.9 ,,2.4 4.3

Table 3 Colour of Sample Additive Days Storage Nil,'-sa1rple nwashed-.- 1.8 4.4' 16.7 46.6 .NiLsarrplewashei 1.3 2.2 6.3 18.8 SEDFamplevnwalsh 1.6 1.4 -1.s 4.5 BED sample-washedu L6 1.5 2.0 3:9

SED Dlsalicylldeneethylenedlamlne.

I claim:

1. A compositionofmat'ter' consisting essentially of a phenol which is liable to oxidative deterioration and, as a stabilizer herefore, a small amount of disalicylideneethylene diamine.

2. The composition of'cl'aim 1 wherein said disalicylidene ethylene diamine is present in an amount from- 0.1 to 1% by weight of said phenol. v i

3. A eompo'sitionas claimed inclaim 1 wherein said phenol is selected from the group consisting of phenyl and alkyl phenols. p

4. Theflcomposition of claim 3 wherein said phenol is ortho phenyl phenol;

5. The composition ofclaim 3 wherein said phenol is para phenyl' phenol.

6. The composition- 'o'f'cl'aim 3 wherein said phenol is 4-methyl-2,6-di-tert. butylphenol.

References Cited as file of thi patent UNITED STATES PATENTS 

1. A COMPOSITION OF MATTER CONSISTING ESSENTIALLY OF A PHENOL WHICH IS LIABLE TO OXIDATIVE DETERIORATION AND AS A STABLIZER HEREFORE, A SMALL AMOUNT OF DISALICYLIDENEETHYLENE DIAMINE. 